typedef struct _D3DMATRIX {
D3DVALUE _11, _12, _13, _14;
D3DVALUE _21, _22, _23, _24;
D3DVALUE _31, _32, _33, _34;
D3DVALUE _41, _42, _43, _44;
} D3DMATRIX, *LPD3DMATRIX;
Describes a matrix for such methods as IDirect3DDevice::GetMatrix and IDirect3DDevice::SetMatrix.
In Direct3D, the _44 element of a projection matrix cannot be a negative number. If your application needs to use a negative value in this location, it should scale the entire projection matrix by -1, instead.